preformed precipitate

例句：

1. 1. The engineer designed the building with preformed steel beams.
   工程师用预先形成的钢梁设计了这座建筑。
2. 2. Thepreformed parts of the machine wereassembled before assembly.
   机器的预成型部件在组装前就已经装配好了。
3. 3. The preformed concrete was poured into the moldand allowed to cure for several days.
   预制混凝土被倒入模具中，经过几天的硬化过程。